1. Field of the Invention
The invention relates in general to an optical module, and more particularly, to an optical module with movable reflective mirrors.
2. Description of the Related Art
Of the many peripherals of a personal computer, the scanner can be said to be essential equipment. Generally speaking, the scanners in today's market have only little difference in terms of function and image scanning quality. Therefore, how to further shrink the size and volume of a scanner to improve the convenience of use has become a focus for R&D engineers in the field of scanners.
Please refer to FIG. 1, a schematic diagram for a conventional optical module. The conventional optical module 100 comprises a carriage 110 and a guiding piece 120, wherein the carriage 110 is equipped with a reflective mirror set, a lens and a photoelectric sensing device (not shown in the diagram).
The carriage 110, which is coupled to the guiding piece 120, can move back and forth along the scan direction D.
In the course of scanning, the image light 130 of the document to be scanned, the reflecting light or the penetrating light of the document to be scanned for instance, enters into the carriage 110. The image light 130, reflected by the reflective mirror set composed of plural reflective mirrors, will be focused via a lens and received by the photoelectric sensing device.
Each reflective mirror of the reflective mirror set, the lens and the photoelectric sensing device are all fixed in the carriage 110. The purpose is to keep both the front optical path and the rear optical path at a fixed value such that a clear and quality scan image can be obtained. The front optical path is the path traveled by the image light, emitted by the document to be scanned, reflected via various reflective mirrors, arriving at the lens lastly. The rear optical path refers to the path from the lens to the photoelectric sensing device, The carriage 10, having to accommodate all reflective mirrors, the lens and the photoelectric sensing device, is undesirably large.
It can be understood from the above disclosure that an over-sized carriage 110 will affect the scanner, which the carriage 110 is installed therein. The consequence is that the overall volume of the scanner cannot be effectively reduced. Moreover, a conventional scanning module whose back focus cannot be enlarged cannot be used to scan large-sized documents.